1. Field of the Invention
The present invention relates to a valve operating system for an engine and, more specifically, to a valve operating system for controlling the opening of an intake and/or exhaust valve in accordance with a vehicle operation parameter.
2. Description of the Related Art
As disclosed in Japanese Patent Public Disclosure (JP A) No. 63-147909, a valve operating system for an engine has been proposed which switches a cam for operating the valve and controlling a valve opening parameter or characteristic, such as the timing of valve opening and closing, valve lift and the like.
The cam for valve operation is switched in accordance with the vehicle operating parameter to change the valve opening parameter to thereby achieve proper intake and exhaust in the engine. However, such conventional valve control does not necessarily provide the proper valve opening characteristic. Furthermore, the conventional control does not allow the limit of the rotational speed of the engine to be increased.